1. Field of the Invention
The present invention relates to a focused ion beam apparatus including a gas field ion source.
2. Description of the Related Art
Conventionally, a liquid metal gallium ion source has been used in a focused ion beam apparatus. The focused ion beam apparatus uses gallium to perform stable beam irradiation, and hence the focused ion beam apparatus has been used for defect repair of a mask used in lithography, for manufacturing a specimen of a transmission electron microscope, and the like. However, there is a problem in that, after ion beam irradiation, gallium may still remain in the specimen.
Further, as an apparatus using nonmetal ion species, a focused ion beam apparatus including a gas field ion source is developed, in which an ion source gas is supplied to a fine emitter, and the ion source gas species adsorbed on the emitter are ionized by a strong electric field generated at a tip of the emitter, to thereby generate an ion beam (see Japanese Patent Publication No. H07-192669). In an apparatus constituted as described above, because a nonmetal gas ion is used as an ion source, there does not occur such a problem that, after beam irradiation, a metal still remains in the specimen.
However, in the conventional focused ion beam apparatus, the ion species of the ion source cannot be switched easily, and hence only one ion species has been used. Therefore, the same ion species has been required to be used in both processing and observation.